I'm storing my lovely 99 996 in my unheated garage for a long Canadian winter.  Should I keep the car cover on it all winter?  Its all polished now and wanted to keep the dust off of it but wondered if keeping a cover on it would cause any condensation build-up (or is it too cold to worry about that?)  I'll be starting it up every 3 weeks or so and will make sure its cooled down before re-covering.  Also my dealer advised me NOT to add fuel stabilizer to the full gas tank, which I have always done to other vehicles.  Comments?  TIA